1. Field of the Invention
The present invention relates to a lens barrel incorporating a light amount adjuster located in the light path of a lens system.
2. Description of the Related Art
Cited Patent Reference 1, for example, has hitherto described this kind of lens barrel cam mechanism. That is, the Cited Patent Reference 1 described technologies relating to a light amount adjusting apparatus located in a light path of an optical system and a camera incorporating therein a light amount adjusting apparatus (hereinafter referred to a “first related-art example”. A camera according to this first related-art example includes an optical system having a first lens group of which light exit surface is formed as a concave surface and a second lens group including a convex surface on which light from the first lens group becomes incident and which can be magnified with its optical iris position between the first lens group and the second lens group. There are also included a filter apparatus having predetermined transmittance located behind the second lens group and which can be moved between the position to open an exposure opening and the position to shut the exposure opening and a control unit for controlling based on the magnified states of the optical system and shutter speeds whether the filter apparatus is to be moved to the position to shut the exposure opening. This camera according to the first related-art example is characterized in that, if the shutter speed becomes higher than a predetermined value in the state in which the filter apparatus is located at the position to open the exposure opening, then the filter apparatus is moved to the position to shut the exposure opening so that the camera becomes able to take a picture at a lower shutter speed.
According to the camera having the above-mentioned arrangement described in the Cited Patent Reference 1, there can be achieved effects in which the arrangement of a shutter diaphragm can be optimized, the occurrence of a shutter light amount difference of the shutter diaphragm can be decreased, more suitable exposure can be executed and the size of the camera can be miniaturized (paragraph [0094] in the Japanese patent specification of the Cited Patent Reference 1). [Cited Patent Reference 1]: Japanese unexamined patent publication No. 2004-252367
However, in the lens barrel having the arrangement described in the Cited Patent Reference 1, since a space between an automatic exposure apparatus and a two group ring is narrowed in the non-shooting mode, slackening is generated in a flexible wiring board and hence such slackening may be absorbed by a space provided in the outside of the two group ring. For this reason, the two group ring needs a large space in its outside and this hinders the lens barrel from being miniaturized. Also, since the flexible wiring board has slackening, the slackened portion is brought in slidable contact with other member so that breaking of wire occurs in the sliding portion or that the sliding portion is damaged unavoidably. Further, when the flexible wiring board is accommodated into the lens barrel, slackening of the flexible wiring board is changed. There is then a disadvantage that stress will be applied to a soldered portion connected to the automatic exposure apparatus.